The invention refers to an ozone pipe for use in an ozone production plant, wherein a plurality of ozone pipes are connected in parallel. Each is provided with a tubular dielectric material encased by a metal jacket electrode, as well as with a high voltage fuse arranged in the interior of the dielectric material and interpolated into the current supply leading to the metal coating of the dielectric material. The high voltage fuse switches off the respective ozone pipe in case of electric overload. The fuse is combined into a structural unit with the dielectric material and the contacts for the current supply.
In the past, it was customary to provide such an ozone pipe with a high voltage fuse arranged in the interior of the tubular dielectric material, as shown in German DE-PS 1 085 860. The fuse consists essentially of a fusion conductor interpolated between the current supply and the metal coating of the dielectric material.
The high voltage fuse guarantees keeping the plant in working order, even during failure of one or several ozone pipes. If short-circuits occur, such as due to bursting of the dielectric material, formation of dust bridges or moisture deposits between the electrodes, etc., the fusion conductor is destroyed by the resulting electric charge exceeding the normal value, thus switching off or disconnecting the respective ozone pipe from the circuit.
Experience has shown that conventional ozone production plants, in the past, provided, for example, with a cutoff current of 1 A in high voltage fuses of the kind mentioned, functioned without any disturbances. However, in the presently constructed larger plants with a great number of ozone pipes--in the order of several hundred--the following disturbances have arisen in series without any discernible reason being understood at the present time:
(a) metal electrodes were melted by an electric arc without the fuses first being activated; and PA1 (b) fuses were activated in large numbers with intact glass pipes.
The melting of metal electrodes without cutoff of the circuit by the fuses leads one to conclude that the quick 1 A fuses utilized were too large, while the disconnecting of intact glass pipes points to an insufficient dimensioning of the same fuses.
When investigating these problems in an ozone production plant with 300 ozone pipes of 15,000 volts, a medium effective current of 230 vA per pipe, whereby the high voltage fuses consisted of fusion conductors of a cutoff current of 1A, the following was found: Due to the transformer dimensioned in accordance with the size of the plant, if a glass pipe suddenly becomes defective, there was, at the breaking point of the glass, a much greater energy in the form of an electric arc transmitted to the metal pipe than was the case in the smaller plants. The given rated voltage and an increased rated current result in an output transmitted by the electric arc of about 25 kW. The current-time period characteristic of a 1 A fuse, however, indicates that the cutoff with a 1.7 rated current only takes place after 10 minutes. This makes the power transmitted to the metal pipe by the electric arc sufficient to melt the pipe without having the fuse disconnect in time.
When investigating the second undesired condition, it was found that the fuses disconnect the circuit with intact glass pipes, if sufficient individual charges otherwise statistically distributed over a period coincide at one point in time. The frequency of the periodic coincidence of individual charges at one point in time increases naturally with the number of the ozone pipes, so that large ozone plants are more susceptible. In such a case, the condenser or glass pipe which has been partially to completely discharged, acts with the presently existing high voltage as a short-circuit, and the resulting charges, brief but extremely high, destroy the fuse. The type of damage to the fuses would point to the conclusion that the peak current values may reach several hundred amperes.
It is the object of the invention to provide an ozone pipe of the type mentioned initially, which is constructed to increase substantially the safety of operation in a large ozone production plant. In particular, on the one hand, the fuse provides a safe decoupling of individual pipes in the case of a disturbance, thus avoiding melting of the metal electrode, and on the other hand, any unwarranted cutoff of intact pipes is eliminated.
The invention accomplishes this in an ozone production plant with a large number of ozone pipes--on the order of several hundred--by providing each ozone pipe with a high voltage fuse with a cutoff current of 0.63 to 0.15 A. (amperes), and additionally with a resistance being provided in series. By the arrangement of resistances, the occurrence of high peak currents is limited by means of electric compensation processes between the glass pipes. Simultaneously, this provides the solution to the second problem, in that the melting of metal tubes is avoided without interrupting the circuit by means of the fuse. The high voltage fuses of lower cutoff power are utilized, guaranteeing certain cutoff of the individual pipe with a short-term overload.
Of particular advantage is the use of elements which change their resistance depending on the current, such as cold conductors or semi-conductors. This guarantees smooth operation of an ozone production plant. The additional energy requirement caused by the resistance amounts to about 2 to 3%. This increase in operating costs is negligible in view of the previously occurring damages.
Since the arrangement of the pipe with the additional resistance permits the generation of additional heat, the pipe is cooled without the use of a supplemental cooling agent. The front of the glass pipe forming the dielectric material, on the end facing away from the current supply, has a nozzle for the supplied medium or agent to be ozonized (air and/or gas). The glass pipe is open at the current supply end, and the annular discharge chamber between the glass pipe and the metal electrode serves as return line for the medium emerging from the glass pipe.
The invention is explained by means of the attached schematic drawings.